Improving the platinum (Pt) mass activity for the oxygen reduction reaction (ORR) requires optimization of both the specific activity and the electrochemically active surface area (ECSA). We found ...that solution-synthesized Pt/NiO core/shell nanowires can be converted into PtNi alloy nanowires through a thermal annealing process and then transformed into jagged Pt nanowires via electrochemical dealloying. The jagged nanowires exhibit an ECSA of 118 square meters per gram of Pt and a specific activity of 11.5 milliamperes per square centimeter for ORR (at 0.9 volts versus reversible hydrogen electrode), yielding a mass activity of 13.6 amperes per milligram of Pt, nearly double previously reported best values. Reactive molecular dynamics simulations suggest that highly stressed, undercoordinated rhombus-rich surface configurations of the jagged nanowires enhance ORR activity versus more relaxed surfaces.
Layered metal oxides including MoO3 and WO3 have been widely explored for biological applications owing to their excellent biocompatibility, low toxicity, and easy preparation. However, they normally ...exhibit weak or negligible near‐infrared (NIR) absorption and thus are inefficient for photo‐induced biomedical applications. Herein, the structural engineering of layered MoO3 and WO3 nanostructures is first reported to activate their NIR‐II absorption for efficient photothermal cancer therapy in the NIR‐II window. White‐colored micrometre‐long MoO3 nanobelts are transformed into blue‐colored short, thin, defective, interlayer gap‐expanded MoO3−x nanobelts with a strong NIR‐II absorption via the simple lithium treatment. The blue MoO3−x nanobelts exhibit a large extinction coefficient of 18.2 L g−1 cm−1 and high photothermal conversion efficiency of 46.9% at 1064 nm. After surface modification, the MoO3−x nanobelts can be used as a robust nanoagent for photoacoustic imaging‐guided photothermal therapy to achieve efficient cancer cell ablation and tumor eradication under irradiation by a 1064 nm laser. Importantly, the biodegradable MoO3−x nanobelts can be rapidly degraded and excreted from body. The study highlights that the structural engineering of layered metal oxides is a powerful strategy to tune their properties and thus boost their performances in given applications.
The structural engineering of layered MoO3 and WO3 nanostructures is reported here to activate their NIR‐II absorption for efficient photothermal cancer therapy. The MoO3−x nanobelts can be used as a robust nanoagent for photoacoustic imaging‐guided photothermal therapy to achieve efficient cancer cell ablation and tumor eradication in the NIR‐II window.
A synergistic N doping plus PO43− intercalation strategy is used to induce high conversion (ca. 41 %) of 2H‐MoS2 into 1T‐MoS2, which is much higher than single N doping (ca. 28 %) or single PO43− ...intercalation (ca. 10 %). A scattering mechanism is proposed to illustrate the synergistic phase transformation from the 2H to the 1T phase, which was confirmed by synchrotron radiation and spherical aberration TEM. To further enhance reaction kinetics, the designed (N,PO43−)‐MoS2 nanosheets are combined with conductive vertical graphene (VG) skeleton forming binder‐free arrays for high‐efficiency hydrogen evolution reaction (HER). Owing to the decreased band gap, lower d‐band center, and smaller hydrogen adsorption/desorption energy, the designed (N,PO43−)‐MoS2/VG electrode shows excellent HER performance with a lower Tafel slope and overpotential than N‐MoS2/VG, PO43−‐MoS2/VG counterparts, and other Mo‐base catalysts in the literature.
An N‐doping plus PO43− intercalation strategy is used to induce high conversion (ca. 41 %) of 2H‐MoS2 into 1T‐MoS2, which is much higher than single N‐doping or PO43− intercalation (ca. 28 % and ca. 10 %, respectively). A scattering mechanism is proposed to illustrate the synergistic phase transformation from 2H phase to 1T phase, confirmed by synchrotron radiation and spherical aberration TEM.
Abstract
Single-atom catalysts are becoming increasingly significant to numerous energy conversion reactions. However, their rational design and construction remain quite challenging due to the ...poorly understood structure–function relationship. Here we demonstrate the dynamic behavior of CuN
2
C
2
site during operando oxygen reduction reaction, revealing a substrate-strain tuned geometry distortion of active sites and its correlation with the activity. Our best CuN
2
C
2
site, on carbon nanotube with 8 nm diameter, delivers a sixfold activity promotion relative to graphene. Density functional theory and X-ray absorption spectroscopy reveal that reasonable substrate strain allows the optimized distortion, where Cu bonds strongly with the oxygen species while maintaining intimate coordination with C/N atoms. The optimized distortion facilitates the electron transfer from Cu to the adsorbed O, greatly boosting the oxygen reduction activity. This work uncovers the structure–function relationship of single-atom catalysts in terms of carbon substrate, and provides guidance to their future design and activity promotion.
Free-standing three-dimensional hierarchical porous reduced graphene oxide foam (RGO-F) was first fabricated by a “dipping and dry” method using nickel foam as a template. Three-dimensional (3D) ...RGO-F with high conductivity provides large porosity compared to conventional graphene films. Polyaniline (PANI) nanowire arrays aligned on the foam (RGO-F/PANI) were synthesized by in situ polymerization. A symmetric supercapacitor with high energy and power densities was fabricated using a RGO-F/PANI electrode. The highly flexible RGO-F/PANI foam can directly serve as an electrode with no binders or conductive additives. Owing to the well-ordered porous structure and high electrochemical performance of the RGO-F/PANI composite, the symmetric device exhibits high specific capacitance (790 F g −1 ) and volumetric capacitance (205.4 F cm −3 ), and it shows a maximum energy density and power density of 17.6 W h kg −1 and 98 kW kg −1 . Moreover, the device possesses an excellent cycle life with 80% capacitance retention after 5000 cycles.
•The fatigue reliability model is established by the strain energy based method.•The traffic flow model is proposed by the data from the weigh-in-motion system.•The fatigue reliability of OSD is ...estimated with those combined effect.
The welding residual stress has a prominent contribution to the fatigue damage in deck-to-rib joints of orthotropic steel decks. To estimate the fatigue reliability of deck-to-rib joints with the combined effect of welding residual stress and stochastic traffic flow, a simplified mechanical model is employed to analyze the combined effect of welding residual stress and vehicle-induced stress. The fatigue reliability assessment is conducted by considering the increases of both the traffic flow and the gross vehicle weight with the strain energy density based method. The results demonstrate that the obtained stochastic traffic flow model agrees well with that measured from the weigh-in-motion system, validating the accuracy of the established stochastic traffic flow model for the fatigue reliability analysis. From the calculated fatigue reliability indices with or without the effect of welding residual stress, it can be concluded that the welding residual stress has a prominent negative influence on the fatigue resistance. The effect of the increase of the gross vehicle weight is more significant than that with the increase of the traffic flow on the fatigue reliability, demonstrating that the growth of the gross vehicle weight has a more detrimental impact on the fatigue service life.
Alloying noble metals with non‐noble metals is a promising method to fabricate catalysts, with the advantages of reduced noble metal usage and excellent activity. In this work, electron‐abundant ...Ir/Rh sites, as highly active centers for the hydrogen evolution reaction (HER), are realized by fabricating Ir1−xRhxSb alloys through the arc‐melting method. The electron transfer from Sb to Ir/Rh makes the latter negatively charged, leading to considerably optimized adsorption for active H species during HER. As a result, the Ir1−xRhxSb alloy exhibits outstanding activity for HER, with an optimized overpotential of 22 mV at 10 mA cm–2 and a Tafel slope of 47.6 mV dec–1. This work provides insights into highly active alloys and sheds light on the utilization of electron‐abundant metal atoms.
A ternary Ir1−xRhxSb intermetallic alloy is prepared through the arc‐melting method, with negatively charged metal sites for the hydrogen evolution reaction.
Porous structure design is generally considered to be a reliable strategy to boost ion transport and provide active sites for disordered carbon anodes of Na‐ion batteries (NIBs). Herein, a type of ...waste cork‐derived hard carbon material (CC) is reported for efficient Na storage via tuning the pore species. Benefiting from the natural holey texture of this renewable precursor, CCs deliver a novel hierarchical porous structure. The effective skeletal density test combined with small angle X‐ray scattering analysis (SAXS) is used to obtain the closed pore information. Based on a detailed correlation analysis between pore information and the electrochemical performance of CCs, improving pyrolysis temperature to reduce open pores (related to initial capacity loss) and increase closed pores (related to plateau capacity) endows an optimal CC with a high specific capacity of ≈360 mAh g−1 in half‐cells and a high energy density of 230 Wh kg−1 in full‐cells with a capacity retention of 71% after 2000 cycles at 2C rate. The bioinspired high temperature pore‐closing strategy and the new insights about the pore structure–performance relationship provide a rational guide for designing porous carbon anode of NIBs with tailored pore species and high Na storage capacity.
A type of waste cork‐derived, hard carbon electrode, with hierarchical porous morphology delivers satisfactory electrochemical performance in Na‐ion batteries (both half‐cells and full‐cells) via tuning the pore species. Detailed pore analysis reveals a clear pore structure–performance relationship to guide the designing of advanced porous carbon anode and the related high temperature pore‐closing strategy can be extended to other pristine open‐pore‐rich carbon.
Oxygen, one of the most abundant elements on Earth, often forms an undesired interstitial impurity or ceramic phase (such as an oxide particle) in metallic materials. Even when it adds strength, ...oxygen doping renders metals brittle
. Here we show that oxygen can take the form of ordered oxygen complexes, a state in between oxide particles and frequently occurring random interstitials. Unlike traditional interstitial strengthening
, such ordered interstitial complexes lead to unprecedented enhancement in both strength and ductility in compositionally complex solid solutions, the so-called high-entropy alloys (HEAs)
. The tensile strength is enhanced (by 48.5 ± 1.8 per cent) and ductility is substantially improved (by 95.2 ± 8.1 per cent) when doping a model TiZrHfNb HEA with 2.0 atomic per cent oxygen, thus breaking the long-standing strength-ductility trade-off
. The oxygen complexes are ordered nanoscale regions within the HEA characterized by (O, Zr, Ti)-rich atomic complexes whose formation is promoted by the existence of chemical short-range ordering among some of the substitutional matrix elements in the HEAs. Carbon has been reported to improve strength and ductility simultaneously in face-centred cubic HEAs
, by lowering the stacking fault energy and increasing the lattice friction stress. By contrast, the ordered interstitial complexes described here change the dislocation shear mode from planar slip to wavy slip, and promote double cross-slip and thus dislocation multiplication through the formation of Frank-Read sources (a mechanism explaining the generation of multiple dislocations) during deformation. This ordered interstitial complex-mediated strain-hardening mechanism should be particularly useful in Ti-, Zr- and Hf-containing alloys, in which interstitial elements are highly undesirable owing to their embrittlement effects, and in alloys where tuning the stacking fault energy and exploiting athermal transformations
do not lead to property enhancement. These results provide insight into the role of interstitial solid solutions and associated ordering strengthening mechanisms in metallic materials.
Noble metal nanomaterials have been widely used as catalysts. Common techniques for the synthesis of noble metal often result in crystalline nanostructures. The synthesis of amorphous noble metal ...nanostructures remains a substantial challenge. We present a general route for preparing dozens of different amorphous noble metal nanosheets with thickness less than 10 nm by directly annealing the mixture of metal acetylacetonate and alkali salts. Tuning atom arrangement of the noble metals enables to optimize their catalytic properties. Amorphous Ir nanosheets exhibit a superior performance for oxygen evolution reaction under acidic media, achieving 2.5-fold, 17.6-fold improvement in mass activity (at 1.53 V vs. reversible hydrogen electrode) over crystalline Ir nanosheets and commercial IrO
catalyst, respectively. In situ X-ray absorption fine structure spectra indicate the valance state of Ir increased to less than + 4 during the oxygen evolution reaction process and recover to its initial state after the reaction.
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